Enclosed trailers for the hauling of freight and motor vehicles are not new to the art. Typically, freight or wheeled vehicles may be carried in the same enclosed trailer, allowing a single wheeled, trailered vehicle to be a versatile addition to the motor fleets of those engaged in moving various types of products over the highway. Conventional enclosed trailers have been used for decades, long before the advent of motorized tractors, for the movement of freight in an enclosure which is to some degree protected from the environment. The enclosure is often nothing more than a six-sided container, rectangular in cross section, mounted on a wheeled chassis. The enclosure sides, floor and top may be of a variety of materials, including wood, metal, flexible materials or fabric curtains. The chief purpose of this type of enclosure is to insure that the cargo is protected from the elemental forces of nature, as well as the hazards of highway travel, such as road dust and grime, gravel and the like.
To maximize the utility of such vehicles, the trailer enclosures tend to be constructed to the maximum height, width and length permitted by the laws of the units of government maintaining the highways over which the vehicles will travel. Such trailers are well suited to carrying freight which is containerized, stackable and palletable. Likewise, such vehicles are suitable for the carrying of completely assembled wheeled vehicles such as automobiles, pick-up trucks and the like. To utilize the cargo space in the interior of such trailers to the fullest, however, methods have been devised to fully utilize the vertical height of the trailers, typically by "stacking" vehicular cargo in multiple layers within the confines of the enclosure.
Previously, it has been taught to install within the trailer enclosure a pair of vehicle tracks. These vehicle tracks are horizontally disposed planar surfaces of a width equal to or greater than that of the conventional automobile or truck tires, and of a length which extends from the forward end of the enclosure to the rearward end of the enclosure. The rearward end of the enclosure is usually equipped with a door to allow access to the internal cargo. The tracks may be articulated at one or more points along their length. Previously, it has been known to vertically support said tracks by a series of hydraulic cylinders with two or more such cylinders disposed on each track, one or more near the forward portion of the track, one or more near the center of the track, and one or more near the rear end of the track. By selectively pressurizing and depressurizing the hydraulic cylinders, the position of the tracks may be raised or lowered within the confines of the enclosure, and the tracks may be tilted to bring the rear edge of the track in somewhat closer proximity to the floor of the trailer to facilitate loading and unloading of the vehicles on the tracks. When the trailer is to be used for hauling non-vehicular cargo, the tracks may be lowered to the limit of travel of the hydraulic cylinders, or alternatively may be raised to the maximum extent of travel of the hydraulic cylinders, thereby moving the vehicle loading tracks to a position less likely to obstruct other cargo when the trailer is used for non-vehicular contents.
In the past, such systems have exhibit numerous shortcomings. Because both single action and multiple action hydraulic cylinders have a fixed physical length when fully retracted, the vehicle tracks cannot be conveniently retracted to a position in close proximity to either the floor or roof of the van. To insure a useful operating range to conventional hydraulic cylinders, such hydraulic cylinders must be of sufficient size to position the vehicles loaded on the tracks to a sufficient height above the floor of such enclosed trailers to allow a second layer of vehicular cargo to be driven into and carried on the floor of the trailer. At the same time, the tracks must be movable to a position somewhat near the floor. Such cylinders typically have a minimum collapsed length which effectively establishes the minimum distance between the tracks and the floor or ceiling of the enclosure. Often these dimensions are unacceptable, and severely restrict the usable cargo space when the vehicle is not used for vehicle hauling.
In addition, single action and multi-action hydraulic cylinders are prone to bleed and fully or partially collapse while under pressure. This necessitates the use of mechanical locking devices in addition to the hydraulic cylinders.
The present invention is designed to overcome these shortcomings, and to insure that the vehicle storage tracks may be retracted to a position in very close proximity to the upper and lower surfaces of the enclosure, thereby maximizing the available cargo space.